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The crystallization mechanism of zeolites remains unclarified to date because of lack of effective techniques in characterizing the local structures of amorphous precursors under synthetic conditions. Herein

Small-pore zeolites are gaining increasing attention owing to their superior catalytic performance. Despite being critical for the catalytic activity and lifetime, postsynthetic tuning of bulk Si/Al ratios of small-pore zeolites has not been achieved with well-preserved crystallinity because of the limited mass transfer of aluminum species through narrow micropores. Here, we demonstrate a postsynthetic approach to tune the composition of small-pore zeolites using a previously unexplored strategy named pore-opening migration process (POMP). Acid treatment assisted by stabilization of the zeolite framework by organic cations in pores is proven to be successful for the removal of Al species from zeolite via POMP. Furthermore, the dealuminated AFX zeolite is treated via defect healing, which yields superior hydrothermal stability against severe steam conditions. Our findings could facilitate industrial applications of small-pore zeolites via aluminum content control and defect healing and could elucidate the structural reconstruction and arrangement processes for inorganic microporous materials.

The efficient separation of hydrogen from methane and light hydrocarbons for clean energy applications remains a technical challenge in membrane science. To address this issue, we prepared a graphene-wrapped MFI (G-MFI) molecular-sieving membrane for the ultrafast separation of hydrogen from methane at a permeability reaching 5.8 × 10 6 barrers at a single gas selectivity of 245 and a mixed gas selectivity of 50. Our results set an upper bound for hydrogen separation. Efficient molecular sieving comes from the subnanoscale interfacial space between graphene and zeolite crystal faces according to molecular dynamic simulations. The hierarchical pore structure of the G-MFI membrane enabled rapid permeability, indicating a promising route for the ultrafast separation of hydrogen/methane and carbon dioxide/methane in view of energy-efficient industrial gas separation.

To understand the degradation mechanism of the copper-ion-exchanged SSZ-13 (Cu-SSZ-13) is of high significance for rationally designing a zeolitic catalyst for ammonia-selective catalytic reduction of NOx (NH3-SCR). In this work, we focused on an Al-rich Cu-SSZ-13 and studied its structural degradation under hydrothermal conditions through a set of characterization techniques, including in situ X-ray diffraction (XRD), pair distribution function analysis and transmission electron microscopy–energy dispersive X-ray analysis (TEM–EDX). The results indicated that the chabazite structure tends to contract in the c direction upon hydrothermal treatment and consequently leads to the collapse of the four-membered ring. Such a structure change then results in the movement of isolated Cu2+ species from the face of the double six-membered ring to its center, which damages the structure further. However, the larger rings (6MRs and 8MRs) partially remain during the structure degradation, which possibly explains that some of the isolated Cu2+ species are alive even when the XRD-detectable crystallinity completely loses. The particle-by-particle observations through TEM–EDX analysis suggested that the occurrence of structural degradation differs remarkably from one individual particle to another. In general, particles with smaller size, having a lower Si/Al ratio and a higher Cu/Al ratio, tend to degrade easily. These results offer a thorough understanding of the structural degradation of Cu-SSZ-13 from the microscopic point of view and point out that the uniformity in composition and particle size of the zeolites plays a critical role in the early-stage degradation.

The micropore volumes and effective pore sizes of two types of silicalite-1 membranes were compared with those of a typical silicalite-1 powder. The silicalite-1 membrane with fewer grain boundaries in the membrane layer showed similar micropore volume and effective pores size to those of the silicalite-1 powder. In contrast, when the silicalite-1 membrane contained many grain boundaries, relatively small micropore volume and effective pore size were observed, suggesting that narrowing and obstruction of the micropore would occur along grain boundaries due to the disconnection of the zeolite pore. The silicalite-1 membrane with fewer grain boundaries exhibited relatively high permeation properties for C6-C8 hydrocarbons. There was an over 50-fold difference in benzene permeance between these two types of membranes. We concluded that it is important to reduce grain boundaries and improve pore-connectivity to develop an effective preparation method for obtaining a highly permeable membrane.

Silicalite-1 membrane was prepared on an outer surface of a tubular &alpha, alumina support by a secondary growth method. Changes of defect amount and crystallinity during secondary growth were carefully observed. The defect-less well-crystallized silicalite-1 membrane was obtained after 7-days crystallization at 373 K. The silicalite-1 membrane became (h0l)-orientation with increasing membrane thickness, possibly because the orientation was attributable to &ldquo, evolutionally selection&rdquo, The (h0l)-oriented silicalite-1 membrane showed high p-xylene separation performance for a xylene isomer mixture (o-/m-/p-xylene = 0.4/0.4/0.4 kPa). The p-xylene permeance through the membrane was 6.52 &times, 10&minus, 8 mol m&minus, 2 s&minus, 1 Pa&minus, 1 with separation factors &alpha, p/o, &alpha, p/m of more than 100 at 373 K. As a result of microscopic analysis, it was suggested that a very thin part in the vicinity of surface played as effective separation layer and could contribute to high permeation performance.

Faujasite (FAU) zeolite membranes were prepared by seed growth method. The polycrystalline zeolite membrane became less porous with the growth of zeolite crystals. The microstructure of the membrane was characterized by SEM and TEM after several rates of crystal growth. In addition, Si/Al ratio was analysed by TEM-EDS. Meso-voids existed in the zeolite membrane after 1-h synthesis, and hexagonal shaped FAU crystals were easily distinguished. Twin relations were quite often observed for the connection between FAU crystals, while they were seldom found in the seed crystals. On the other hand, crystals lost hexagonal shape with further synthesis time. Moreover, the density of twin relations became less. While voids could hardly being observed by SEM in the zeolite membrane, there existed intercrystalline boundaries formed by two crystals of different orientation. Microstructures of these boundaries were directly observed by HREM. Si/Al ratio of the zeolite membrane was close to 1, which is smaller than that of seed crystals (Si/Al = 2.5). Step growth at the twin boundary was firstly observed. This growth process is assumed to be the key growth mechanism in densification of the polycrystalline zeolite membrane. Finally, densification process of zeolite membrane is proposed based on the microscopic analysis.

Zeolite Y is one of the most important catalysts that are used in catalytic processes such as fluidic catalytic cracking (FCC). This zeolite can be degraded during the FCC process, particularly under high-temperature steaming conditions; however, the degradation mechanisms have not been fully elucidated yet and previous studies have mainly focused on dealumination behaviors. In this study, we performed high-temperature treatments under steaming conditions to prepare a series of degraded zeolite Y samples, which were carefully investigated through techniques such as argon adsorption, high-energy X-ray total scattering, and transmission electron microscopy. A non-linear correlation between the crystallinity and micropore volume was observed. We propose that the degradation mechanism involved the formation of a dense amorphous layer, which the argon molecules cannot infiltrate into, on the surface of the crystals during high-temperature steaming treatment.

Copper-ion-exchanged SSZ-13 has been demonstrated to be an effective catalyst for the ammonia selective catalytic reduction of NOx. However, the Cu-SSZ-13 is still susceptible to hydrothermal degra...

Carbon molecular sieve (CMS) membranes were prepared on the outer surface of porous ceramic tubes using a lignin-based material, organosolve-lignin, and a phenol resin, Bellpeal-S899, as precursors. Higher pyrolysis temperature resulted in higher hydrogen selectivity over oxygen or other larger gases, but hydrogen permeance decreased significantly. On the contrary, addition of a small amount of iron(III) acetate basic to the precursors improved the hydrogen selectivity but maintained the hydrogen permeance. Addition of iron compound to the precursor strongly reduced the permeances of nitrogen and methane through the resulting CMS membranes. Distribution of iron in the carbon matrix was evaluated by transmission electron microscopy energy dispersive X-ray spectroscopy (TEM-EDS) and electron probe microanalyzer (EPMA). The influence of aging on the membrane permeance was also studied. The results suggest the possibility to tune the size of ultra-micro-pores in CMS membranes using additives.

Electron microscopy combined with theoretical calculations was applied for the precise analysis of countercations within zeolitic nanocavities. We observed a light element (Na + ) within an LTA type zeolite under low dose conditions. The aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM) mode has high sensitivity for small undulations in atomic potentials within a crystalline specimen. Two types of Na + were distinguishably imaged by AC-HRTEM. Delocalized Na + within an eight-membered ring (8MR) of LTA type zeolite could be imaged as a torus shape. Ab initio molecular dynamics simulations supported such delocalization of the Na + . In contrast to Na + , Cs + was located at the center of the 8MR because of its cationic size and the inner spacing of the 8MR.

Zeolites possessing novel structures and compositions have been produced using guest organic species, which are called organic structure-directing agents (OSDAs). However, the specific roles of OSDAs have not been clarified yet. In this work, *BEA- and CHA-type zeolites are synthesized from the same starting inorganic materials but with different OSDAs, and the crystallization pathways are observed using various analytical techniques. During the synthesis of *BEA-type zeolite, the gradual evolution of the aluminosilicate structure leads to the transformation from an amorphous structure to a crystalline one. On the other hand, during the synthesis of CHA-type zeolite, a few CHA nuclei are formed in “partially-ordered amorphous species” and grow through the consumption of “buffer amorphous species” on the surfaces of CHA-type zeolite crystals. This clear difference in crystallization behaviors of the two zeolites under the same synthetic conditions is attributed to the differences in the structure-directing...

This study investigated the permeation behaviors of n-hexane and 2-methylpentane through two-types of silicalite-1 membranes that have different pore-connectivity. The permeation mechanisms of these hydrocarbons were able to be explained by the adsorption–diffusion model. In addition, the fluxes through silicalite-1 membranes could be expressed by the modified Fick’s first law. The hydrocarbon fluxes through S-1S with better pore-connectivity were ca. 3–20 times larger than those through S-1M with poor pore-connectivity. For these membranes with different pore-connectivity, the activation energy of diffusion of n-hexane was 17.5 kJ mol−1 for the membrane with better pore-connectivity and 18.0 kJ mol−1 for the membrane with poorer pore-connectivity, whereas for 2-methylpentane it was 17.9 and 33.0 kJ mol−1, respectively. We concluded that the pore-connectivity in silicalite-1 membrane significantly influences the molecular diffusivities.

Design of efficient and environmentally benign zeolitic materials at the nanoscale is becoming increasingly important for a range of industrial applications. Here we report a high resolution transmission electron microscopy investigation of the atomic level structure of zeolite beta synthesized without an organic structure-directing agent (OSDA). Direct visualization of zeolite beta crystals confirmed them to be essentially defect free, with domain boundaries the only disruption to the pore channel network. Direct visualization enabled the distribution of BEA and BEB polytype subdomains to be quantified, and the overall abundance ratio was calculated to be BEA:BEB = 9:11. By assuming this ratio corresponds to the probability of forming a new BEA or BEB layer on a (001) surface at the tip of a crystal, the experimentally observed polytype distributions can be described by a simple probability function, suggesting that epitaxial crystal growth occurs stochastically in a state close to chemical equilibrium.

Phosphorus-modified zeolite with an intergrowth structure of AFX and CHA (P-AFX/CHA) was synthesized by a triple-template system. The synthesis system involved two nitrogen-containing organic structure directing agents (N-OSDAs, N,N,N-trimethyl-1-adamantammonium hydroxide and 1,1'-(1,4-butanediyl)bis(1-azonia-4-azabicyclo[2,2,2]octane) dibromide) for developing the intergrowth zeolite phase. Tetraethylphosphonium cation (TEP) was also added as a phosphorus-modifying agent. The calcination treatment causes the decomposition and oxidation of TEP to form a phosphorus oxide species that interacts with the zeolite framework, thereby realizing direct-phosphorus modification in the zeolite cavity. We optimized the synthesis condition of P-AFX/CHA, tuning the synthesis gel composition and selecting the counter anion in TEP, and found that tetraethylphosphonium bromide (TEPBr) is useful for effectively incorporating phosphorus into the intergrowth zeolite. 31P magic angle spinning (MAS) NMR confirmed the phosphorus modification via the decomposition of P-OSDA, whereas X-ray diffraction and transmission electron microscopy revealed the intergrowth structure. In addition, 13C dipolar decoupling (DD) MAS NMR, elemental analysis, and other synthesis results suggested the selective modification of phosphorus into the CHA phase in the intergrowth zeolite. Phosphorus modification was effective in improving the thermal stability of P-AFX/CHA. The thermal stability increased with increasing the phosphorus modification degree.

High-silica erionite (ERI) zeolites are conventionally synthesised via a so-called charge density mismatch (CDM) approach, and a typical synthesis takes several days to complete. We herein demonstrate an ultrafast route to synthesise high-silica erionite zeolites in as short as 2 h at 210 °C. The fast-synthesised ERI has been proved to show higher hydrothermal stability compared with the conventionally synthesised product.

Structures of platinum and chromium supported on zeolite beta were investigated by XAFS, XPS, UV–vis, NH3-TPD, XRD, CO chemisorption, and molecular dynamics simulation. Both platinum and chromium were uniformly dispersed in the micropore of zeolite beta. Loading of chromium helped platinum to disperse highly and stabilized in the micropore of beta. Major species of platinum on PtCr/beta after calcination at 773 K was Pt2+ forming a Pt–O bond. The Pt–O bond disappeared, and a Pt–Pt bond did not appear by reducing PtCr/beta in hydrogen, accompanying formation of Pt0. Chromium was loaded as chromate anion in the micropore of zeolite. Results of molecular dynamics simulation showed that Pt2+ associated with CrO42– in the micropore of zeolite beta was more stable than those in the absence of chromium species. We concluded that CrO42– electrostatically stabilizes Pt2+ and inhibits migration and aggregation of platinum.

Catalysis of Pt/beta zeolite catalyst modified via the addition of various elements (Ca, Cr, Mn, Fe, Co, Ni or Cu) for n-heptane skeletal isomerization was investigated at 513 K in a conventional flow reactor with a fixed catalyst bed. It was found that, among the catalysts tested, PtCr/beta was the most promising, since its use resulted in relatively high yields of multi-branched alkanes in conjunction with a very low selectivity for cracking products. Ion exchange was found to be an effective method for the addition of chromium to zeolite, compared to the evaporation to dryness process. Platinum particle sizes were observed using STEM. While particles ~10–30 nm in size were evident on the surface of Pt/beta, they were rarely observed on the PtCr/beta catalyst. It was concluded that platinum homogeneously dispersed within beta zeolite micropores resulted in the observed decreased cracking activity during n-heptane isomerization and that the addition of chromium had been effective in increasing degree of platinum dispersion.

SAPO-34 membranes were hydrothermally synthesized using 75 nm-sized SAPO-34 crystals as seed crystals. The SAPO-34 membrane showed a high selectivity to water for water/2-propanol (H 2 O/IPA) vapor permeation (separation factor>3200). Selective coke deposition within the pores of SAPO-34 via methanol-to-olefins reaction was applied to examine the effects of zeolitic and non-zeolitic pathways on the separation properties using various SAPO-34 membranes with different qualities. The results imply that H 2 O molecules are selectively adsorbed and the permeation of IPA is blocked even through the non-zeolitic pores (less than 1 nm) of SAPO-34 membranes. The size and hydrophilicity of non-zeolitic pores are important factors for inhibiting the IPA permeation.

Silica containing uniformly dispersed Ni nanoparticles has been synthesized by a precursor solution method, involving heat treatment and reduction stages, and the transformation of the Si–Ni–O precursor into the composite powder has been investigated systematically to determine the formation mechanism of the nanoparticles. During heat treatment, nickel oxide nanoparticles are found to form simultaneously with the Si–O network, as decomposition of the alkoxy ligand and nucleation of NiO nanoparticles, both occur at around 300°C. The formation of ionically bound Si–Oδ−–Niδ+ units plays a key role in anchoring the NiO in the Si–O network and impeding further crystalline growth. Moreover, the formation of the Si–O2−–Ni2+ interactions in the composite of dispersed NiO in SiO retard the reduction of NiO, resulting in a characteristic microstructure consisting of highly dispersed metallic Ni nanoparticles within an Si–O matrix. This nickel–silica composite is expected to show enhanced reversible hydrogen adsorption, making it attractive for use in separation membranes with high hydrogen selectivity.

This study reports a unique and novel method of preparation of Ag/CeO2 catalyst for carbon oxidation. A calcination of physical mixture of Ag metal powder and CeO2 at 500 °C results in self-dispersion of Ag into nano-particles on CeO2. From TEM images, the average diameter of Ag particles in Ag power before calcination was around 66 nm, while the particle size of Ag became smaller around 8 nm with very narrow distribution. Oxygen vacancy on CeO2 surface is suggested to play an important role in the self-dispersion of Ag. The obtained catalyst showed high activity for soot oxidation comparable to Ag/CeO2 prepared by impregnation method. The promotion effect of CeO2 was not observed in physical mixtures with Cu, Au and Pt. Mechanical mixtures of Ag and various metal oxide supports were also examined. The addition of Ag to CeO2, SnO2, ZrO2, ZnO, TiO2, and Nb2O5 significantly lowered the temperature of carbon oxidation than those of supports, while that to Co3O4, CaO, La2O3, NiO, SiO2, Al2O3 and MgO did not.

MCM-22 membranes were prepared on a porous α-alumina tube using a secondary growth technique consisting of the deposition of seed crystals on a substrate followed by crystal growth under hydrothermal conditions. In this study, two types of seed crystals, MCM-22 and ITQ-2, were used. The MCM-22 membrane prepared using ITQ-2 seed crystals (MCM-22 (I) membrane) was composed of MCM-22 polycrystals with a thickness of 5 μm, which is much thinner than that of the MCM-22 membrane prepared using MCM-22 seed crystals (MCM-22 (M) membrane) (15–20 μm). Vapor permeation of water/acetic acid mixtures through the MCM-22 membranes was studied. The MCM-22 (I) membranes calcined at 400 °C showed a high separation factor of 78 with a water permeance of 4 × 10−8 mol m−2 s−1 Pa−1 at 120 °C. Elevating the calcination temperature to 500 °C resulted in a lower separation factor. The MCM-22 (I) membrane calcined at 400 °C has a hydrophilic internal surface due to the presence of silanol groups within the framework that contribute to the high selectivity to water permeation.

Organic template-free synthesis of nano-zeolite has been an important subject of both scientific and industrial applications. Most research has focused on the fabrication of nano-zeolite by a bottom up approach, that is, control of zeolite nucleation and crystal growth during the hydrothermal synthesis. This communication reports a new method for the production of nano-zeolite powder by a top-down approach. In this study, the zeolite was first milled to produce a nanopowder. This technique can cause destruction of the outer portion of the zeolite framework and hence cause pore blocking, which deactivates various properties of the zeolite. To remedy this, the damaged part was recrystallized using a dilute aluminosilicate solution after bead milling. As a result of the combination of bead milling and postmilling recrystallization, nano-zeolite A (LTA type zeolite) about 50 nm in size with high crystallinity was successfully obtained.

The reversible hydrogen adsorption site in Ni-nanoparticle-dispersed amorphous silica (Si-O) was identified by analyzing the hydrogen adsorption behavior and the microstructure. The total amount of reversibly adsorbed hydrogen was evaluated from the total surface area of Ni and the Ni concentration in the composite. The total surface area of the Ni nanoparticles in each sample powder was calculated from the mean particle size of the Ni nanoparticles in the Si-O matrix using dark field images taken by transmission electron microscopy and high-angle annular dark-field images by scanning transmission electron microscopy. The estimated amount of reversibly adsorbed hydrogen was highly consistent with that obtained experimentally by hydrogen adsorption analysis, which suggested that reversible hydrogen adsorption occurred at the Ni/Si-O interface.

Highly stable Al-MCM-48-type mesoporous materials with zeolitic secondary building units (SBUs) of BEA zeolite in the framework (hereafter denoted as Al-MCM-48-BEA) were synthesized by direct hydrothermal methods. The synthesis involves simultaneous introduction of two types of structure directing agents, namely, tetraethylammonium hydroxide (TEAOH) for controlling the fabrication of SBU of BEA and a mixture of cetyltrimethylammonium bromide (CTMABr) and Brij-30 for directing the formation of cubic mesophase. The results of X-ray diffraction (XRD) and fourier-transform infrared (FT-IR) spectroscopy revealed the coexistence of mesoporous Al-MCM-48-type arrays with Ia –3 d cubic structure zeolitic SBUs in the materials. In addition, two distinct types of pore systems with characteristics of meso- and micropores were identified in Al-MCM-48-BEA materials by using variable-temperature (VT)-hyperpolarized (HP) 129 Xe NMR spectroscopy. Thus, Al-MCM-48-BEA materials possess SBUs of BEA in the walls of highly ordered cubic mesoporous arrays and therefore exhibit much higher thermal, hydrothermal, and mechanical stabilities in comparison to conventional Al-MCM-48 materials. Consequently, these novel materials were found to have strong acidic sites, rendering them highly active and selective catalysts for the formation of α-tocopherol (vitamin E) in the alkylation–condensation of isophytol with trimethylhydroquinone under supercritical CO 2 media.

Hydrothermally stable Al-MCM-48 with variety of Si/Al ratios and Al-MCM-41 with tunable pore sizes were successfully obtained from pre-heated aluminosilicate gel precursor. They showed the higher acid strength and hydrothermal stability comparing with conventional ones. Thus, this synthetic strategy offers a straightforward and convenient access to mesoporous aluminosilicates with zeolite-like acidity and stability.

Single-crystalline platinum nanocubes with porous morphology were synthesized for the first time by using ethylene glycol, HCl, and polyvinylpyrrolidone as the reducing agents of H2PtCl6. The morphology and size distribution of the Pt particles formed were studied with a high-resolution transmission electron microscope and selected-area electron diffraction pattern. By controlling the material concentrations and reaction temperature and period, Pt single crystals about 5 nm in size were formed in the first stage of the reduction process that had {100} facets, which were stacked one on top of the other, forming porous nanocubes 20-80 nm in length. The synthesized Pt nanocubes exhibited enhanced catalytic activity for methanol oxidation.

In this study, a simple anodic oxidation process resulted in the successful synthesis of novel N-ion-doped TiO(2) with one-dimensionally aligned and large-sized mesopores. TiO(2) obtained by this anodic oxidation process possessed the high values of specific surface area and a large amount of one-dimensional mesopores with 30-50 nm diameter. Furthermore, X-ray photoelectron spectroscopy and UV-vis results suggested the possibility that these TiO(2) products were composed of a N-ion-doped powder. Thus, novel structured TiO(2) with large-sized mesopores was simply synthesized by an anodic oxidation of Ti metal in a nitric acid solution. These uniquely nanostructured mesoporous TiO(2) products will expand possibilities for applying mesoporous TiO(2) in new fields.

A comprehensive study on a series of highly stable calcium containing mesoporous aluminosilicate molecular sieves (CaAlMMSH) having different acidic properties has been made by varying the Si/Ca ratio in synthesis gels. The structural, physical, and porous properties of these microporous/mesoporous composite materials were characterized by X-ray diffraction, N2 adsorption/desorption isotherm measurements, solid-state 27Al and 29Si magic angle spinning NMR, and variable-temperature hyperpolarized 129Xe NMR, Fourier transform infrared (FTIR) and diffuse reflectance FTIR spectroscopies. As compared to the parent AlMMSH materials, the incorporation of excessive amount of calcium tends to result in an overall increase in acid amount while at the expense of strong acid sites. The CaAlMMSH materials were found to have superior catalytic activities than AlMMSH in the amidation of palmitic acid with N-hexadecylamine. However, no significant enhancement in catalytic activity for the esterification of palmitic acid ...

This article reports the structural variation of SBA-type mesostructured silica formed from a mixture of tetraethyl orthosilicate (TEOS), alkyltrimethylammonium bromides, and 1,3,5-trialkylbenzenes under acidic conditions. Swollen 2D hexagonal mesophases were formed from the silica source and hexadecyltrimethylammonium bromide (C16TAB) with varying amounts of trimethylbenzene (TMB) and triethylbenzene (TEB), whereas drastic structural changes were observed with triisopropylbenzene (TIPB). Characterization by X-ray diffraction and transmission electron microscopy observation revealed that the mesophase was changed from hexagonal p6mm to cubic Pm3n to cubic Fm3m with increasing amounts of TIPB. Thus, the addition of TIPB leads to the preferential formation of spherical micelles rather than the swelling of rodlike micelles. When tetradecyltrimethylammonium bomide (C14TAB) was used, similar structural changes were triggered by smaller amounts of TIPB; however, almost no structural change was observed when octadecyltrimethylammonium bromide (C18TAB) was used. These findings provide a better understanding of the roles of 1,3,5-trialkylbenzenes in the structural control of silica-alkyltrimethylammonium mesophases.

Zeolites possess excellent ion exchange capabilities, so that it is easy to synthesize Ag-zeolite (Ag x Al x Si 1―x O 2 ) using an AgNO 3 aqueous solution. When this Ag type zeolite is irradiated with a high energy electron beam of several hundred keV in a TEM, the chemical bonds in the zeolite crystal are broken and the crystal eventually becomes amorphous. (L. A. Bursill, E. A. Lodge and J. M. Thomas: Nature 286 (1980) 111― 113.) We have found that ordered clusters of Ag atoms are formed in the amorphous region during this process. It is anticipated that quantum effects will appear in this material. (Y. Nozue, T. Kodaira and T. Goto: Phys. Rev. Lett. 68 (1992) 3789.).

In this study, the syntheses of bulks of Y-zeolite were attempted by a hydrothermal hot-pressing (HHP) method with various conditions such as the amounts and concentrations of NaOH solution, reaction temperatures, and reaction times. Dense bulks of Y-zeolite were successfully obtained by this HHP method. Under an optimum synthetic condition of HHP, solidified bulks of Y-zeolite possessed translucency with high values of specific surface area. Transmission electron microscopy observation of these translucent bulks of Y-zeolite showed that their microstructures were densified like polycrystalline ceramics sintered by heat treatments and no amorphous phase was observed at the boundaries of Y-zeolite grains. As a result, in these unique bulks of Y-zeolite synthesized by the HHP method, the microporous network was thoroughly connected at the grain boundaries of Y-zeolite.

Oriented ZSM-5 seed crystals on an α-Al2O3 porous substrate were hydrothermally treated in a raw sol. The ZSM-5 membranes were fabricated via secondary growth of the seed crystals. For some samples, the seed-applied substrate was fired at 300 or 600 °C before the secondary growth in order to enhance adhesion between the substrate and the seed crystals. The influence of the firing on the subsequent secondary growth of the seed crystals was examined by XRD, SEM, and TEM. The TEM images of the sample fired at 300 °C showed that the resulting membrane was continuous, and in the membrane, large ZSM-5 particles were distributed in a porous matrix. The ZSM-5 particles were slightly smaller than the used seed crystals. HR-TEM observations showed that the porous matrix is comprised of ZSM-5 micro-crystals, and the part adjacent to the large ZSM-5 crystals has the same crystallographic orientation as the large crystals. The TEM images of the sample fired at 600 °C showed that the resulting layer is comprised of particles with a core-shell structure. The core consisted of ZSM-5 micro-crystals, whereas the shell was composed of large ZSM-5 rod-like crystals. It is inferred that the formation of these interesting microstructures is related to the degradation of the template agent, NPr4OH, in the seed crystals by firing at 300 and 600 °C. The part including no template is dissolved by a hydrothermal treatment, and the dissolved species is re-crystallized via reaction with a template agent in the used raw sol, resulting in the formation of interesting microstructures.

The attractive properties of zeolites, which make them suitable for numerous applications for the energy and chemical industries and for life sciences, are derived from their crystalline framework structures. Herein, we describe the rational synthesis of a microporous material, HUS-10, utilizing a layered silicate precursor, HUS-2, as a structural building unit. For the ordered micropores to be formed, interlayer pillars that supported the original silicate layer of HUS-2 were immobilized through the interlayer silylation of silanol groups with trichloromethylsilane and a subsequent dehydration-condensation reaction of the hydroxyl groups on the preintroduced tetrahedral units. An actual molecular sieving ability, enabling the adsorption of molecules smaller than ethane, was confirmed in the ordered micropores of HUS-10. The hydrophilic adsorption could also be controlled by changing the number of methyl and hydroxyl groups in the immobilized interlayer pillars. In addition, when the adsorption behaviors of CO2, CH4, and N2 on HUS-10 were compared to those on siliceous MFI and CDO zeolites with approximately the same pore diameter, the CO2 adsorption capacity of HUS-10 was comparable. Conversely, because of the adsorption inhibition of CH4 and N2, HUS-10 exhibited larger CO2/CH4 and CO2/N2 adsorption ratios relative to those of MFI and CDO zeolites. These results reveal that the unique microporous framework structure presented by the rational structural design using the layered silicate precursor HUS-2 has the potential to separate CO2 from gas mixtures.

Catalytic oxidation of multi-walled carbon nanotubes (MWNCTs) with some noble metal nanoparticles was observed by environmental transmission electron microscopy (E-TEM). Amoeba-like movement of the nanoparticles was observed even at a temperature of ∼400°C, which is much lower than the melting points of any of the metals. In particular, rhodium particles reacted intensely with MWCNTs, and assumed a droplet-like shape. On the other hand, gold particles caused very little erosion of the MWCNTs under the conditions of this study.

Both YBa 2 Cu 3 O 7− x (Y123) and GdBa 2 Cu 3 O 7− x (Gd123) layers with BaZrO 3 (BZO) rods were deposited on Hastelloy tapes with textured buffer layers (CeO 2 /Gd 2 Zr 2 O 7 ) using pulsed-laser deposition (PLD). Two volume percent of YSZ–Y123 and 2 vol%YSZ–Gd123 were used as target materials. The critical current density ( J c ) values of these layers in a magnetic field parallel to the substrate normal were enhanced compared with those of Y123 layers without BZO rods. In the entire incident angle of magnetic fields, the J c reduction of the Gd123 layer with BZO rods were improved compared to that of the Y123 layer with BZO rods. Transmission electron microscopy was used to characterize the nanostructures of the specimens prepared by both focused ion beam and standard ion milling. The Y123 layer with BZO rods and the Gd123 layer with BZO rods were composed of c -axis oriented grains, in which BZO rods aligned in the [0 0 1] of Y(Gd)123 ware distributed homogeneously. The diameter of the BZO rods was about 5 nm and the rods grew from the CeO 2 interface to the surface. The orientation relationships between Y(Gd)123 and BZO were as follows: (0 0 1)Y(Gd)123//(0 0 1)BZO and (1 0 0)Y(Gd)123//(1 0 0)BZO. In the Gd123 with BZO rods, a high density of stacking faults in the (0 0 1) plane and distorted (0 0 1) planes were found. The formation of the BZO rods in the Y(Gd)123 and a high density of defects with respect to the (0 0 1) plane in the Gd123 were considered to enhance the J c values in high magnetic fields.

We have succeeded in the fabrication of distorted cubic R-3m mesoporous silica film with 3D open mesostructure providing high pore accessibility from the surface-air interface of the film. The film fabrication involves a unique approach of adding 1,3,5- triisopropylbenzene (TIPB) to the silica/cetyltrimethylammoniumbromide (CTAB) coating sol during its preparation. The addition of TIPB induces the formation of spheroid micelles, promoting R-3m mesostructure in the film. This phase does not exist in the corresponding binary phase diagram of CTAB surfactant.

We report the fabrication of cubic Ia3d mesoporous silica thin films via a new approach involving mesophase transformation induced by the degradation of organic moiety from the film during calcination. The mesoporous silica film is synthesized using tetraethyl orthosilicate (TEOS) as a silica source and a diblock copolymer (Brij-30) as a structure-directing agent under acidic conditions. Control of mesophase selection and its orientation in a mesoporous silica thin film appears to be possible by the induced phase transformation approach reported here.